docs: def _check_lambda(self):
          """Check if lambda function exists.
  
          Returns:
              True if function does exist
              False if function does not exist
          """
          exists = False
          try:
              self.lambda_client.get_function(FunctionName=self.app_name)
              exists = True
          except boto3.exceptions.botocore.exceptions.ClientError:
              pass
          return exists